On June 14, 2008, an outbreak of gastroenteritis occurred among elementary school students in Incheon. We conducted an investigation to identify the source and described the extent of the outbreak. We performed a retrospective cohort study among students, teachers and food handlers exposed to canteen food in the elementary school. Using self-administered questionnaires we collected information on symptoms, days of canteen food eaten, food items consumed. Stool samples were collected from 131 symptomatic people and 11 food handlers. The catering kitchen was inspected and food samples were taken. Of the 1,560 people who ate canteen food, 117 were symptomatic cases, and the attack rate was 7.5%. Consumption of cucumber-crown daisy salad (RR=2.71), fresh cabbage mix (RR=2.23), dried radish salad (RR=3.04) and young radish kimchi (RR=2.52) were associated with illness. Sixty-four (45%) of the 142 stool specimens were positive for Norovirus. Norovirus was detected in 2 food handlers. Interviews with kitchen staff indicated the likelihood of contamination from an infected food handler to the dried radish salad during food processing. The excretion of Norovirus from asymptomatic food handlers may be an infection source of Norovirus outbreaks.
The rural areas are the main outbreak sites of severe fever with thrombocytopenia syndrome (SFTS). To identify the seroprevelance of SFTS in rural island, we conducted a serosurveillance study of SFTS virus (SFTSV) of the general public in Mui Island, a representative rural island of Incheon, South Korea. A total of 203 participants (female 127, male 76, 30 to 97 years old, median 67) without symptoms or signs of SFTS were collected via a convenience sampling. Nested reverse transcription PCR was conducted for both the S and M segments of SFTSV gene. Indirect immunofluorescence assay was also performed for immunoglobulin G (IgG) and immunoglobulin M (IgM) against SFTSV. Only 1 participant (0.5%) was positive to SFTSV gene without IgM against SFTSV. In addition, 12 participants (5.9%) were positive to IgG against SFTSV. Seropositive rate of IgG against SFTSV was higher in age group >65 than ≤65 (9.6% vs. 1.1%, OR 9.202; 95% CI, 1.165-72.692; p=0.026) and was not statistically significant according to sex, occupation and duration of residence in Mui Island. This study suggests that SFTSV readily have infected humans in the rural island of Incheon, South Korea. Therefore, reinforced surveillance about SFTS is needed, focusing on medically vulnerable area such as an island.
This study aimed to characterize the seasonal abundance of hard ticks that transmit severe fever with thrombocytopenia syndrome virus from April to November 2019 and 2020 on Ganghwa-do, Incheon Metropolitan City, Korea. The ticks were collected at grassland, grave site, copse and mountain road using a collection trap method. The ixodid hard ticks comprising three species (Haemaphysalis longicornis, H. flava, and Ixodes nipponensis) collected were 6,622 in 2019 and 3,811 in 2020. H. longicornis was the most frequent (97.9% in 2019 and 96.0% in 2020), followed by H. flava (2.0% and 3.0% in 2019 and 2020, respectively) and I. nipponensis (less than 0.1%). Our study demonstrated that seasonal patterns of the tick populations examined for two years were totally unsimilar. The hard ticks tested using RT-qPCR were all negative for severe fever with thrombocytopenia syndrome virus.
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